Rectifier



I. LEVIN RECTIFIER April 10, 195 1 Original Filed Feb. 8, 1945 INVENTOR.

- IRVIN LEVIN 91M I/fi/AV Patented Apr. 10, 1,951

UNITED STATESPATENT OFFICE RECTIFIER Irvin Levin, Baltimore, Md. Original application February 8, 1945, Serial No.

576.864 now Patent No. 10, 1949. Divided and th 14, 1946, Serial No.

2,469,393, dated May is application January *5 Claims. (Cl. fi -366.)

(Granted under the act of March 3, 1883, as

amended April 30,

The dry disc type rectifier field at present comprises three different types of rectifiers, namely, the copper sulphide, the copper oxide and the selenium. W 7

An obj ect of my invention is to provide a method of construction of a dry disc type rectifier which can be easily assembled in the laboratory.

Another object of my invention is to provide a method of construction of the discs which are more easily formed chemically.

Another object of m invention is t provide a method of construction of an iron oxide-magnesium dry rectifier, in which the purity of the iron does not have to be important.

invention was conceived by the need of a 'dis'c tyipe rectifier which couldeasily be made in the laboratory. My dry -disc -type rectifier is easier to form chemically in the laboratory than the copper oxide, copper sulphide and the selenium types. Only a flame 'o'rother source of heat is required for the "formation of the iron oxide barrier layer, whose chemical name isierroso-ferric oxide, whereas in the copper oxide and copper sulphide types critical temperatures and e manipulations are required. The purity of the iron does not appear to be as important a problem as with the copper used in the copper containing rectifiers. In fact, the iron oxide-magnesium rectifiers can utilize mild steel or other ordinary steels commonly met with. The iron and magnesium discs can be at least as thin as 5 mils. The iron disc is heated at red heat for about three minutes on a sheet of asbestos mounted on a tripod by using a Bunsen flame or other source of heat. This allows a layer of the magnetic ferroso-ferric oxide to form over the surface of the iron disc. The iron disc is allowed to cool to the black color. The magnesium disc, which has a clean surface, is placed on the hot iron disc which contains the ferroso-ferric layer, pressed together immediately and the combination allowed to cool. The combination is assembled as a rectifier unit and tested for its D. C. to A. C. ratio. 0.636 is the limiting value of this ratio for perfect half-wave 2 rectification. However, an oscilloscope check may be performed or even substituted for the above ratio test.

If the combination is found to rectify poorly, it is removed from the assembly and reheated carefully with a flame or other source of heat with the magnesium disc resting on top of the unit. Great caution is needed to prevent the melting or burn* ing of the magnesium.

The rectifying layer can carry a current density (and rectify), as read on a "D. C. meter, of.'25"0 milliamperes per square inch, which is the maximum optimum amount. The D. to A. ratio change very little with temperature, which rises to approximately 40 C. at the above current density of 250 milliamperes per square inch. All frequencies used were cycles per second, butit does not necessarily mean that the frequency is limited to 60 cycles. Raising the voltage over the optimum maximum value does not impair the rectifying action when brought back to normal.

My invention will be more fully understood from the following detailed description taken in connection with the accompanying drawing wherein I have shown a preferred embodiment thereof In the drawings, Figure 1 is an exploded view of a rectifier embodying my .ip'resent invention; and

Figure 2 is an elevational view of said rectifier when in its assembled operative condition.

In the drawing, Figure 1 shows an exploded view of my invention comprising; bolt 10., steel washers l I. radiator electrodes 12:, iron disc with an oxide layer [3, magnesium disc I4, insulating gasket l5 and nut It. The holes in steel washers H and insulating gasket I5 are of small diameter so as to be closely fitted around bolt It). When the rectifier is assembled the bolt [0 is co'-axially centered in the larger diameter holes of the radiator electrodes l2, iron disc with an oxide layer l3 and magnesium disc l4, so as to allow the current to enter only at wire terminal ll, pass through the iron disc with an oxide layer l3 in contact with the magnesium disc l4 and the circuit is completed through the rectifier at terminal I 8 without making electrical contact between bolt l0, radiator electrode l2 adjacent to insulating gasket l5, and said discs 13 and I4.

Figure 2 shows a complete rectifier assembly comprising: an iron disc with an oxide layer I3 in surface contact with a magnesium disc l4, radiator electrodes I2, suitable insulating gasket I5 and metal Washers II. This assembly as shown is clamped securely by bolt Ill and nut l6, said bolt and nut l6 insulated from the rectifying circuit as shown and described in Figure 1. Electrical connections I! and I8 are made to the radiator electrodes 12 for connecting the rectifier in an electric circuit for rectifying purposes.

Having thus described my invention I desire to secure by Letters Patent and claim:

1. A rectifier of the class described comprising in combination, an input electrode, an electrode element having one face engaging said input electrode and having an oxide layer on the opposite face thereof, a, second electrode element of magnesium having one face heat bonded to said oxide layer, an output electrode engaging the opposite face of said second electrode element, and means for holding said electrodes and elements in said engaged relation.

2. A rectifier of the class described comprising in combination, an input electrode, a metal disc having one face engaging said input electrode and having an iron oxide layer on the opposite face thereof, a second disc of electropositive metal having a considerably lower melting point than the first mentioned disc and having one face fused to said oxide layer, an output electrode engaging the opposite face of said second disc. and means for holding said discs and electrodes in said engaged relation.

3. A rectifier of the class described comprising, in combination, a metal plate providing an input electrode and having an effective radiation area and a central perforation, a metal disc having a central perforation and one face engaging said metal plate and having an iron oxide layer on the opposite face thereof, a second disc of mangesium having a central perforation and one face heat bonded to said iron oxide layer, a second metal plate providing an output electrode and having an effective radiation area and a central perforation, and clamping means including an element extending through said perforations for holding said elements in said engaged relation.

4. A rectifier of the class described comprising, in combination, a metalplate providing an input electrode and having an effective radiation area and a central perforation, an iron disc having a central perforation and one face engaging said metal plate and having an iron oxide layer on the opposite face thereof, a second disc of magnesium having a central perforation andone face heat bonded to said iron oxide layer, a second metal plate providing an output electrode and having an effective radiation area and a central perforation, and clamping means for holding said elements in said engaged relation comprising a boltmember extending axially through the perforations in said elements and out of contact therewith, a metallic washer adjacent to the input electrode for applying clamping pressure thereto, an insulating gasket adjacent to the output electrode and a second metallic washer engaging the outer face of said insulating gasket for applying clamping pressure to the output electrode and threaded means connected with the bolt member for clamping the assembly together.

5. A rectifier of the class described comprising, in combination, a metal plate providing an input electrode and having an effective radiation area and a central perforation, an iron disc having a central perforation and one face engaging said metal plate and having a ferroso-ferric oxide layer on the opposite face thereof, a second disc of magnesium having a central perforation and one face heat bonded to said ferroso-ferric oxide layer, a second metal plate providing an output electrode and having an effective radiation area" and a central perforation, and clamping means for holding said elements in said engaged relation comprising a bolt member extending axially through the perforations in said elements and out of contact therewith, a metallic washer adjacent to the input electrode for applying clamping pressure thereto, an insulating gasket adjacent to the output electrode and a second metallic washer engaging the outer face of said insulating gasket for applying clamping pressure to the output electrode and threaded means connected with the bolt member for clamping the assembly together.

IRVIN LEVIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,640,335 Grondahl Aug. 23, 1927' 1,751,361 Ruben Mar. 18, 1930 1,751,460 Ruben Mar. 18, 1930 1,865,213 Ruben June 28, 1932 2,221,773 Berman Nov. 19, 1940 2,239,770 Becker et a1 Apr. 29, 1941 FOREIGN PATENTS Number Country Date 379,538 Great Britain Sept. 1, 1932 

